How has LCA been applied to 3D printing? A systematic literature review and recommendations for future studies

Previously perceived as a rapid prototyping technique, additive manufacturing (AM) has evolved into a fully developed manufacturing process, with growing accessibility to different industrial sectors. Its technological and economic advantages are frequently documented, but AM's environmental performance is seldom investigated. Not long ago discrete initiatives to assess AM's applicability for building large-scale structures started to arise. Mostly focused on technical and economic feasibility, these studies pave the way for the process's consolidation in the construction sector. This paper aims to systematically and critically assess the available literature on AM's life cycle environmental impacts and to identify the main challenges and trends on loads measurements. The findings help feed recommendations to perform life cycle assessments (LCA) in AM initiatives, with a special focus on the construction sector. A systematic search led to the careful analysis of 52 papers, out of 353 that matched our search protocol. In terms of LCA methods' robustness, a lack of transparency stood out in many papers, suggesting that authors were most likely non-LCA experts, applying the tool without much knowledge of requirements and modelling intricacies. In terms of documented global warming potential (GWP) values in comparison to conventional manufacturing (CM), AM processes were portrayed as beneficial in most cases. Most papers documented results ranges, which represented different printing, production or distribution strategies, in which AM's performance varied considerably. LCA played a significant role in finding an optimum production approach and seems to be a valuable lens to assure 3D printing's environmental competitiveness. A contribution analysis showed that there is a shift between materials vs. production processes contribution in the life cycle GWP loads of systems manufactured with AM and CM. 3D printing processes account for almost 80% of AM's total GWP, while for CM that position is held by the material-related loads. For construction related AM processes, the material intensity is, however, still by far the largest contributor to building systems' GWP, maintaining the impact distribution as in typical manufacturing processes. (C) 2019 Elsevier Ltd. All rights reserved.